(a) Field of the Invention
This invention relates to improvements in the electrodeposition of metals. More particularly it relates to a method for improving the efficiency of metal electrowinning and electrorefining processes.
In electrodeposition processes for metals using anodes and cathodes, such as, for example, the electrowinning of such metals as zinc, copper, nickel, manganese, cadmium, lead and iron, and the electrorefining of such metals as copper, lead, nickel, silver, gold, bismuth and antimony, the cell commonly used is an elongated, substantially rectangular, box-like structure. The cell contains the electrolyte, and is generally provided with suitable means for ingress and egress of the electrolyte, which is generally circulated continuously. The electrodes are placed in the cell, transverse to its length, and suitably supported. They are also provided with electrical current, being connected to a power source by means of bus bars, contact bars, or other current distribution means. Generally, all of the electrodes in the cell are spaced the same distance apart, the precise spacing used being dependent upon a number of factors. With the electrodes thus equally spaced along the length of the cell, it is generally considered that the amount of current supplied to the cell is approximately equally distributed between the electrodes in the cell. In this way, an average value for the current density in the cell can be readily computed.
(b) Description of the Prior Art
The alignment of the electrodes in such electrolysis cells is of considerable importance. If the electrodes are improperly aligned, electrode warping, corrosion and shorting can all occur, resulting in prematurely short electrode life and also in a loss of current efficiency. Many means have been developed to ensure that the electrodes are both properly spaced and properly aligned. Such means are of a great variety of designs. Typical examples are to be found in the following United States patents:
U.S. Pat. No. 1,206,963, Robert L. Whitehead, 1916.
U.S. Pat. No. 1,206,964, Robert L. Whitehead, 1916.
U.S. Pat. No. 1,206,965, Robert L. Whitehead, 1916.
U.S. Pat. No. 1,276,208, Julius H. Gillis, 1918.
U.S. Pat. No. 2,115,004, William H. Bitner, April 26, 1938.
U.S. Pat. No. 2,443,112, Fernando Alfred Morin, June 8, 1948.
U.S. Pat. No. 3,579,431, Peter M. Jasberg. May 18, 1971.
U.S. Pat. No. 3,697,404, Peter M. Paige, October 10, 1972.
U.S. Pat. No. 3,997,421, Roland Perri, December 14, 1976.
U.S. Pat. No. 4,035,280, Richard Deane et al, May 12, 1977.
In these last two patents, a spool shaped notched contact-bar, and anode spacer clips are described which, when used in conjunction with suitable electrodes, provide a stable three dimensional array of anodes and cathodes in electrolytic cells.
However, even when adequate precautions are taken to ensure both proper alignment and proper spacing of electrodes, electrical difficulties are still experienced. Shorting between electrodes, overheating of electrodes, warping of electrodes and other consequent problems are encountered, which lead to losses of both current efficiency and productivity. In an extreme case, shorting can lead to localised melting of electrodes.